Anatomy
- Terminal branch of the lateral cord, root values C5 to C7
- Pierces coracobrachialis about 5 cm below the coracoid, with wide variation
- Runs between biceps and brachialis
- Continues as the lateral cutaneous nerve of the forearm, emerging lateral to the biceps tendon at the elbow
- Fibres can travel with the median nerve, so injury patterns vary
Motor Supply
- Coracobrachialis
- Biceps brachii
- Brachialis, with a radial nerve contribution to its lateral part
Sensory Supply
- Lateral forearm through the lateral cutaneous nerve of the forearm
Clinical Features
- Isolated injury is rare, seen with penetrating trauma, shoulder dislocation and strenuous exercise
- Weak elbow flexion and supination with an absent biceps reflex
- Numbness of the lateral forearm
- The lateral cutaneous nerve of the forearm can be compressed by the biceps aponeurosis
- Heavy weight training can compress it within coracobrachialis
Investigations
- EMG of biceps and brachialis
Management
- Observe closed injuries for recovery
- Oberlin transfer of an ulnar nerve fascicle to the biceps branch restores elbow flexion in upper trunk brachial plexus injuries
Structures at Risk
- Retraction of the conjoint tendon in the deltopectoral approach
- Coracoid transfer in the Latarjet procedure
- Lateral cutaneous nerve of the forearm during anterior distal biceps repair, the most frequent nerve complication of that operation
Reviewed by Professor Phong Tran, Head of Orthopaedic Surgery, Western Health. Last updated 10 October 2026.